[Qemu-devel] Re: [PATCH] char: Flush read buffer in mux_chr_can_read

[Jan Kiszka <jan.kiszka@siemens.com>]

Alexander Graf wrote:
> On 12.05.2010, at 20:51, Jan Kiszka wrote:
> 
>> Alexander Graf wrote:
>>> Jan Kiszka wrote:
>>>> Alexander Graf wrote:
>>>>
>>>>> Jan Kiszka wrote:
>>>>>
>>>>>> Move the buffer flush from mux_chr_read to mux_chr_can_read. While the
>>>>>> latter is called periodically, the former will only be invoked when new
>>>>>> characters arrive at the back-end. This caused problems to front-end
>>>>>> drivers whenever they were unable to read data immediately, e.g.
>>>>>> virtio-console attached to stdio.
>>>>>>
>>>>>>
>>>>> I don't see this patch applied, but also don't see any issues with
>>>>> virtio-console anymore on today's git. Odd.
>>>>>
>>>>>
>>>> Hmm, I had a clear before-after experience using virtio console with an
>>>> x86 Linux guest. I still think my patch is correct and required. Maybe
>>>> you can bisect this positive "regression"? Something might paper over
>>>> the core issue now.
>>>>
>>> I just did a git reset --hard on
>>> baf0b55a9e57b909b1f8b0f732c0b10242867418 and it worked! What the ...
>> Whatever "worked" now means (I'm slightly confused), I just rechecked
>> the situation over current git head ("qemu linux-guest.img -chardev
>> stdio,id=cons,mux=on -device virtio-serial -device
>> virtconsole,chardev=cons -mon chardev=cons", "cat /dev/hvc0" in the
>> guest, typing some chars on the host console): The problem still
>> persists, my patch still solves it. Can you confirm this, ideally also
>> for s390?
> 
> Now that I can finally reproduce the bug with --enable-io-thread, I can verify that it does *not* fix the issue.

I do not trust your tests. :p

I just tried to reproduce with --enable-io-thread and the setup I
described above - all still fine here. Can you reproduce with an x86 guest?

Jan

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